I would very rarely use "I will bet". Naturally, even when talking about the future, I would say "I bet". "I bet that I can..." --> "I believe I can..." It would be strange to say that you *will* believe something in future. I would always say "I bet that I can..." EXCEPT for: "I will bet $10 on..." This is talking about betting money "I will bet on X soccer team winning if X player is on their team" if your belief is dependant on a condition. Please ask if that's unclear! Mich https://www.italki.com/michelle

"I bet" expresses an actual action. "I'll bet" or "I will bet" express the (strong) desire/conviction to bet.

I bet refers to now- I bet on horses. I'll bet on horses later or possibly next week. ( in the near future )

Walkabout, thanks for your explanation. That really helped me.

I agree with the others. However, in your example, you are not actually betting money. "I bet" is a figure of speech. (Admittedly, there are some men who would actually bet money on whether they could get a woman to go out with them, but most women wouldn't appreciate that. It's a crude thing to do.) "I will bet" sounds a bit awkward unless you are referring to actual betting situations, e.g., horse races, card games, football teams, etc. "I will bet you $10 that I can do 100 push-ups without stopping." "I will bet on the next horse race" (as in "I plan to" place a bet...). You can also use the present tense, "I bet" for actual betting situations. "I bet you $10 that I can do 100 push-ups without stopping." In any event, #1 sounds more natural than #2.